Copolyamides containing caprolactam, lauriclactam and 11-aminoundecanoic acid

ABSTRACT

The invention relates to copolyamides containing caprolactam, lauriclactam and 11-aminoundecanoic acid, useful as heat sealing agents.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of out application Ser. No.384,371, filed July 31, 1973, now U.S. Pat. No. 3,883,487 granted May13, 1975.

This invention relates to copolyamides containing caprolactam,lauriclactam and 11-aminoundccanoic acid together with furtherpolyamide-forming components as basic units, to a process for producingthese copolyamides and to their use for heat-sealing.

BACKGROUND OF THE INVENTION

Copolyamides of the basic units caprolactam, lauriclactam and11-aminoundecanoic acid are known from DOS 1,595,591. In melt form,these ternary polyamides show high bond strength which is used in thetextile industry for heat-sealing fabrics. In addition to high bondstrength, these copolyamides show high resistance to solvents of thekind used for dry-cleaning textiles, and to the washing temperatures ofup to about 80°C normally encountered in the textile industry.Unfortunately, this resistance is largely governed by a high content oflauriclactam and/or 11-aminoundecanoic acid. Although the resistance ofthe copolyamides to washing at elevated temperatures increases withincreasing content of these basic units, their melting temperature isalso increased with the result that conventional copolyamides cannot beused for heat-sealing temperature-sensitive substrates such as leather,temperature-sensitive natural and/or synthetic materials, non-wovenfabrics, felts, tufted fabrics and the like. Substances melting belowabout 115°C, below 110°C or even below 105°C, are required forheat-sealing temperature-sensitive substrates of this kind.

SUMMARY OF THE INVENTION

The object of the invention is to find substances which are suitable forheat-sealing temperature-sensitive substrates, show high bond strengthat low sealing temperatures and during subsequent cooling and whichnevertheless are highly resistant to chemical cleaning agents.

The invention relates to copolyamides containing caprolactam,lauriclactam and 11-aminoundecanoic acid as basic units, which aredistinguished by the fact that they contain as an additional basic unita hexamethylene diamine salt of an aliphatic dicarboxylic acid of theformula

    HOOC--(CH.sub.2).sub.n --COOH                              (I)

in which n is the number 4, 7, 8, 10 or 11, the basic units beingincorporated in the copolymer by polymerisation in the followingproportions:caprolactam 20-40% by weightlauriclactam 20-35% byweight11-aminoundecanoic acid 15-35% by weighthexamethylene diamine saltofthe acid of formula (I) 15-40% by weight

The invention also relates to a process for producing copolyamidescontaining caprolactam, lauriclactam and 11-aminoundecanoic acid asbasic units, distinguished by the fact that the aforementioned basicunits and, as additional basic unit, a hexamethylene diamine salt of analiphatic dicarboxylic acid, corresponding to the formula (I) in which nis 4, 7, 8, 10 or 11, are polymerised under pressure at elevatedtemperature in the following quantitative proportions:

    caprolactam        20-40% by weight                                           lauriclactam       20-35% by weight                                           11-aminoundecanoic acid                                                                          15-35% by weight                                           hexamethylene diamine salt                                                                       15-40% by weight                                           of the acid of formula (I)                                                

by methods known per se.

The copolyamides defined above are used for heat-sealing. Surprisingly,they have an extremely low melting point of below 110°C, generally below100°C and, in some cases, even below 90°C. Despite these low meltingpoints, they show extremely high bond strength after heat-sealing atelevated temperature and, on the other hand, a high resistance tochemical cleaning agents, i.e. solvents and cleaning agents of the kindadded to aqueous cleaning solutions. Accordingly, substrates heat-sealedwith the copolyamides according to the invention show high resistance towater-containing cleaning agents, even at elevated washing temperatures.

Accordingly, the copolyamides according to the invention can be usedwith advantage for heat-sealing temperature-sensitive substrates.

Copolyamides of the kind whose basic units are incorporated in thecopolymer in the following proportions:

    caprolactam        25-35% by weight                                           lauriclactam       ˜30% by weight                                       11-aminoundecanoic acid                                                                          18-25% by weight                                           hexamethylene diamine salt                                                                       15-30% by weight                                           of the acid of formula (I)                                                

are preferred for the purposes of the invention. The followingquantitative proportions are particularly preferred:

    caprolactam        ˜30% by weight                                       lauriclactam       ˜30% by weight                                       11-aminoundecanoic acid                                                                          ˜20% by weight                                       hexamethylene diamine salt                                                                       ˜20% by weight                                       of the acid of formula (I)                                                

The acids of general formula (I) have the following names:

n = 4, adipic acid

n = 7, azelaic acid

n = 8, sebacic acid

n = 10, dodecane dicarboxylic acid

n = 11, brassylic acid.

The acids of formula (I) in which n is 6, 7, 8 or 10 are particularlypreferred for the purposes of the invention, acids in which n is 7 or 8being particularly preferred because they are readily availablecommercial products and lead to copolyamides which can be used withparticular advantage for heat-sealing.

According to the invention, the copolyamides are produced by methodsknown per se. As in the production of C12-polyamide from lauriclactam,temperatures of from about 280° to 300°C, preferably of about 290°C, andpressures of from about 10 to 50 atms, preferably from 15 to 30 atms,are generally used. Polymerisation is continued for several hours underthese conditions and is preferably followed by after-condensation for afew hours, preferably for about 1 to 3 hours, at 250° to 300°C. Thecatalysts, chain terminators and/or other additives and the processconditions normally used for the polymerisation of lauriclactam areemployed. More particularly, polymerisation is best carried out in theabsence of air, i.e. in an inert gas atmosphere. The copolyamidesaccording to the invention are preferably used for heat-sealing in theform of fine powders which are applied to the substrates to be bonded. Asuitable viscosity of the copolyamide where it is used for theproduction of films is best in the range from about 1.4 to 1.5 Thisnumber denotes the solution viscosity of a 0.5% solution of thecopolyamide in m-cresol at 25°C.

The copolyamides used in accordance with the invention can contain otheradditives, for example dyes, in the usual way.

The copolyamides used in accordance with the invention are copolymerswhich are formed during the polymerisation of a mixture of the polyamideformers. The basic units are condensed into the polymer chain instatistical distribution. The surprising effects described are notobtained in cases where the polyamide formers are polymerised separatelyfrom and then melted together with the polyamides.

The copolyamides according to the invention can also have smallquantities of other polyamide formers condensed into them.

For reasons of ready accessibility and satisfactory reproducibility ofproduction to form copolyamides with uniform properties, it is generallynot advisable to add further polyamide formers.

It is possible by means of the copolyamides according to the inventionto bond substrates of many different kinds, particularlytemperature-sensitive substrates to substrates of the same or differenttype. A copolyamide according to the invention is preferably introducedin the form of powder between the surfaces to be bonded. The copolyamidecan of course also be used in the other forms, for example films,filaments or chopped filaments. The substrates are then pressed atelevated temperature. The pressing temperature is governed primarily bythe temperature-sensitivity of the substrate. Since the copolyamidesaccording to the invention develop outstanding bond strength even atvery low sealing temperatures of, for example, from about 100° to 130°Cor up to 150°C in dependence upon their melting range, it is possible toapply extremely low sealing temperatures. Cooling to room temperature isaccompanied by hardening so that the bonded substrates are firmlyunited. There is no need for drying or evaporation of solvents.

The copolyamides according to the invention in the form of powders canbe applied to a substrate to be bonded, for example by the powdercoating machines normally used in the coating industry. In thisconnection, it is also possible to coat only selected areas of thesubstrate surface with the copolyamide powder according to theinvention. Examples of substrates to be bonded include textiles ofnatural materials and/or synthetic materials such as wool, silk, cottonand polyesters, polyamides and the like. Other temperature-sensitivesubstrates such as leather, plastics films and the like, can also beheat sealed using the copolyamides according to the invention.

The copolyamides of the invention can be mixed with plasticizers beforebeing used. Suitable plasticizers are, e.g., sulfonic acid derivativesof the following formula ##SPC1##

wherein R₁ stands for hydrogen or methyl, and R₂ for hydrogen, a loweralkyl group, or a cyclohexyl group.

Particularly preferred are benzene- or toluene-sulfonic acid ethylamide. Corresponding commercial products can be obtained. Suchcommercial products are, e.g., mixtures of p- and o-toluene sulfonicacid alkyl amides. Phenol carboxylic acid or alkyl esters thereof mayalso be employed as plasticizers. Examples thereof are butyl-p-hydroxybenzoate, lauryl-p-hydroxy-benzoate, p-oxy-benzoic acid,octyl-p-oxybenzoate. Bisphenol A and similar compounds may also beemployed as plasticizers. Of course, it is necessary to use in each caseplasticizers which are compatible with, or suitable for, the particularcopolyamides employed, as is well understood by persons skilled in theart. The plasticizers can be worked into the copolyamides by mixing themwith the latter and heating the mixture at temperatures above themelting point. At these temperatures they can, e.g., be extruded, inorder to serve for the manufacture of threads, foils, and the like.Powders can also be produced.

When the copolyamides are employed in powder form, it is sometimessuitable to disperse these copolyamide powders in aqueous dispersions,to apply such dispersions, e.g., to textile parts to be joined,especially materials inserted in clothing, e.g., by point coating, thento dry the textiles thus coated, to sinter them, to fix them, and toheat-seal them to the materials to be joined, e.g., by ironing thetextiles with a flatiron or with an ironing press (cf., e.g. GermanPats. No. 2,007,971 and No. 2,229,308). The dispersions usually containthickeners and stabilizers in order to produce stable dispersions. Suchthickeners and stabilizers are well known to the artisan, e.g.,polymeric organic acids, long-chain fatty acids, and the like. It ispractical to make the dispersions slightly alkaline. When suchdispersions are used, it is particularly preferred not to mix theplasticizers with the copolyamides, as described above, but to add theplasticizers as a further component to the dispersions.

The quantity of plasticizers may amount up to about 50% by weight of thetotal quantity of copolyamide and plasticizer. Particularly preferred isan amount of plasticizer up to about 25% by weight with relation to thetotal quantity of copolyamide and plasticizer.

It has already been pointed out above that the copolyamides of theinvention may also contain a dyestuff or other customary additives.Thus, the copolyamides may contain, e.g., customary antioxidants,anti-inflammable agents, and particularly optical brighteners as well asfluorescence-causing agents. A wide variety of such agents, which can beobtained as commercial products, are known in the art. Of course, onlyadditives which are resistant to the heat-sealing temperatures appliedcan be employed.

DESCRIPTION OF PREFERRED EMBODIMENTS EXAMPLE 1

300 parts by weight of caprolactam, 200 parts by weight of11-aminoundecanoic acid, 300 parts by weight of lauriclactam, 200 partsby weight of AH-salt (adipic acid hexamethylene diamine salt) and 12parts by weight of adipic acid as polymerisation-degree regulator, areweighed into an autoclave equipped with stirring mechanism, a gas inletand a gas outlet. The atmospheric oxygen present inside the autoclave isremoved by repeated rinsing under pressure with purified nitrogen.

The reaction mixture is heated to 290°C and the increasing pressureinside the autoclave limited to 25-30 atms by correspondingly settingthe valve. The reaction mixture is stirred for 3 hours under theseconditions. The pressure is then reduced to normal pressure over aperiod of 2 hours.

The reaction mixture is then aftercondensed with stirring for 2 hours inthe absence of pressure under a gentle stream of nitrogen.

On completion of the pressure-free aftercondensation phase, thetemperature is lowered to 160°-180°C and the melt spun through a nozzlein the form of a monofil by means of a gear pump, cooled and granulated.

The resulting granulates have a melting range of from about 90° to 95°C,as measured on a KOFLER heating-stage microscope.

EXAMPLE 2

The following polyamide-forming monomers are reacted under thepolycondensation conditions described in Example 1: 200 parts by weightof caprolactam, 250 parts by weight of 11-aminoundescanoic acid and 250parts by weight of lauriclactam, 300 parts by weight of 6,10-salt, 12parts by weight of adipic acid. The resulting copolyamide has a meltingrange of from about 85° to 90°C, as measured on a KOFLER heating-stagemicroscope.

EXAMPLE 3

A copolyamide is prepared from the following components in the same wayas described in Example 1: 250 parts by weight of caprolactam, 250 partsby weight of 11-aminoundecanoic acid, 250 parts by weight oflauriclactam, 250 parts by weight of the salt of azelaic acid andhexamethylene diamine, 12 parts by weight of adipic acid. A copolyamidewith a melting range of from about 84° to 88°C is obtained.

EXAMPLE 4

The following monomer combination: 350 parts by weight of caprolactam,200 parts by weight of 11-aminoundecanoic acid, 300 parts by weight oflauriclactam, 150 parts by weight of 6,12-salt and 12 parts by weight ofadipic acid, gives a copolyamide with a melting range of 95° to 105°Cunder the same polycondensation conditions as in Example 1.

EXAMPLE 5

A copolyamide with a melting range of 90° to 100°C is obtained from thefollowing components under the same polycondensation conditions as inExample 1: 300 parts by weight of caprolactam, 300 parts by weight of11-aminoundecanoic acid, 200 parts by weight of lauriclactam, 200 partsby weight of 6,13-salt, 12 parts by weight of adipic acid.

EXAMPLES 6 to 21

Copolyamides were prepared from the starting components specified inTable 1 below in accordance with the procedure described in Example 1.The following abbreviations were used:

6 = caprolactam

11 = 11-aminoundecanoic acid

12 = lauriclactam

6,6 = AH-salt (adipic acid hexamethylene diamine salt)

6,9 = hexamethylene diamine azelaic acid salt

6,10 = hexamethylene diamine sebacic acid salt

6,12 = hexamethylene diamine dodecane dicarboxylic acid salt

6,13 = hexamethylene diamine brassylic acid salt

The melting temperatures of the copolyamides obtained are also shown inTable 1.

In the individual Examples, the quantities in which the basic units areused can generally be varied by about ± 3% or at least by 1.5% withoutadversely affecting the properties of the resulting copolyamides to anyappreciable extent.

                                      Table 1                                     __________________________________________________________________________    Monomer composition                                                                %   %   %   %   %   %   %   %                                            Example                                                                            6   11  12  6,6 6,9 6,10                                                                              6,12                                                                              6,13                                                                              Melting range °C                  __________________________________________________________________________     6   35  35  20  10  --  --  --  --  100 - 105                                 7   35  20  30  15  --  --  --  --  103 - 108                                 8   30  30  20  20  --  --  --  --   98 - 104                                 1   30  20  30  20  --  --  --  --  90 - 95                                   9   25  40  20  15  --  --  --  --  105 - 110                                10   25  25  25  25  --  --  --  --   95 - 100                                11   20  25  25  --  30  --  --  --  83 - 89                                   3   25  25  25  --  25  --  --  --  84 -  88                                 12   30  20  30  --  20  --  --  --  88 - 95                                  13   30  15  20  --  35  --  --  --  85 - 90                                  14   35  35  20  --  --  10  --  --  100 - 108                                15   35  20  30  --  --  15  --  --   97 - 107                                16   30  20  30  --  --  20  --  --  90 - 95                                  17   30  25  25  --  --  20  --  --  82 - 90                                  18   30  30  20  --  --  20  --  --  90 - 95                                  19   25  25  25  --  --  25  --  --  85 - 90                                   2   20  25  25  --  --  30  --  --  86 - 91                                  20   30  20  30  --  --  20  --  --   95 - 100                                21   35  20  30  --  --  15  --  --   95 - 105                                 4   35  20  30  --  --  --  15  --   95 - 105                                 5   30  30  20  --  --  --  --  20   90 - 100                                __________________________________________________________________________

COMPARISON TEST

In this comparison test, the bond strength of a copolyamide according tothe invention is compared with that of a copolyamide containing only thebasic units caprolactam, 11-aminoundecanoic acid and lauriclactam.

A copolyamide is prepared as described in Example 1 from the followingmonomer constituents: 25% by weight of caprolactam, 25% by weight of11-amino-undecanoic acid, 25% by weight of lauriclactam, 25% by weightof azelaic acid hexamethylene diamine salt and 2% by weight of azelaicacid as polymerisation-degree regulator. A transparent polyamide meltingat 80° to 90°C, as measured on a KOFLER heating-stage microscope, andhaving a melt index at 130°C of 22, as measured in accordance with DIN53 735, is obtained.

For comparison, a ternary copolyamide is prepared from the followingconstituents: 34% by weight of caprolactam 33% by weight of11-aminoundecanoic acid, 33% by weight of lauriclactam and 1.5% byweight of azelaic acid as polymerisation degree regulator. A copolyamidemelting at 110 to 115°C and having a melt index of 22, as measured inaccordance with DIN 53 735, is obtained.

The polyamides were each ground while cooling and separated by siftinginto a fraction of 0 to 200 mm.

The two powder fractions were applied to a conventional interliningmaterial in an 11-mesh pattern in an amount of 16±1 g per m² by means ofa powder pointing machine of the kind normally used in the coatingindustry.

The coated interlinings thus obtained were ironed with apolyester/cotton fabric under a constant pressure of 350 p/cm² in anelectrically heated ironing press of the kind commonly used in thegarment industry, both the plate temperature and the contact time beingvaried.

The delamination strengths of 2.5 cm wide laminate strips were measuredwith a tension tester.

The delamination strengths (p/2.5 cm) specified in Table 2 weremeasured:

                                      Table 2                                     __________________________________________________________________________    Contact                                                                             Plate temperature of the ironing press (°C)                      time                                                                          (seconds)                                                                           110 120 130 140 150 160 170                                             __________________________________________________________________________          300 400 500 700 1000                                                                              900 900 Invention                                    6                                                                                  --  --  100 200 400 300 300 Comparison                                        400 500 800 1100                                                                              1000                                                                              1100                                                                              1600                                                                              Invention                                   10                                                                                  --  --  200 300 400 500 500 Comparison                                        450 700 900 1200                                                                              1400                                                                              1400                                                                              1300                                                                              Invention                                   15                                                                                  --  --  250 350 500 700 600 Comparison                                        600 900 900 1300                                                                              1500                                                                              1400                                                                              1700                                                                              Invention                                   18                                                                                  --  --  300 600 500 600 750 Comparison                                  __________________________________________________________________________

It can be seen from the Table that extremely good adhesion is obtainedeven at very low plate temperatures of the ironing press, i.e. at verylow scaling temperatures of 110° and 120°C, whereas no adhesion isobtained with the conventional copolyamide at these scalingtemperatures. The conventional copolyamide only produces firm adhesionat higher sealing temperatures.

What is claimed is:
 1. A composition of matter comprising a copolyamideconsisting essentially of recurring units of caprolactam, lauriclactam,11-aminoundecanoic acid and a hexamethylene diamine salt of an aliphaticdicarboxylic acid corresponding to the formula

    HOOC--(CH.sub.2).sub.n --COOH                              (I)

in which n is 4, 7, 8, 10 or 11, said units being incorporated in thecopolyamide in the following proportions:caprolactam 20-40% byweightlauriclactam 20-35% by weight11-aminoundecanoic acid 15-35% byweighthexamethylene diamine salt ofthe acid of formula (I) 15-40% byweight and a plasticizer which is compatible with a suitable forplasticizing said copolyamide.
 2. The composition according to claim 1,wherein the units are incorporated in the copolyamide in the followingproportions:

    caprolactam       25-35%      by weight                                       lauriclactam      about 30%   by weight                                       11-aminoundecanoic acid                                                                         18-25%      by weight                                       hexamethylene diamine salt                                                    of the acid of formula (I)                                                                      15-30%      by weight.                                  


3. The composition according to claim 1, wherein the units areincorporated in the copolyamide in the following proportions:

    caprolactam       about 30% by weight                                         lauriclactam      about 30% by weight                                         11-aminoundecanoic acid                                                                         about 20% by weight                                         hexamethylene diamine salt                                                    of the acid of formula (I)                                                                      about 20% by weight.                                    


4. The composition according to claim 1, wherein n in formula (I) standsfor the number 4, 7, 8 or
 10. 5. The composition according to claim 4,wherein n in formula (I) is 7 or
 8. 6. A process for the production of aheat bonding composition comprising the steps of polymerizingcaprolactam, lauriclactam, 11-aminoundecanoic acid and hexamethylenediamine salt of an aliphatic dicarboxylic acid corresponding to theformula

    HOOC--(CH.sub.2).sub.n --COOH                              (I)

in which n is 4, 7, 8, 10 or 11, under pressure at elevated temperaturein the following quantitative proportions:

    caprolactam         20-40% by weight                                          lauriclactam        20-35% by weight                                          11-aminoundecanoic acid                                                                           15-35% by weight                                          hexamethylene diamine salt of                                                 the acid of formula (I)                                                                           15-40% by weight                                      

thereby forming a copolyamide, and incorporating a plasticizer into saidcopolyamide which is compatible with and suitable for plasticizing saidcopolyamide.
 7. A process according to claim 6, wherein the basic unitsare polymerised in the following quantitative proportions:

    caprolactam       25-35%      by weight                                       lauriclactam      about 30%   by weight                                       11-aminoundecanoic acid                                                                         18-25%      by weight                                       hexamethylene diamine salt                                                                      15-30%      by weight                                       of the acid of formula (I).                                               


8. A process according to claim 6, wherein the basic units arepolymerised in the following quantitiative proportions:

    caprolactam       about 30%   by weight                                       lauriclactam      about 30%   by weight                                       11-aminoundecanoic acid                                                                         about 20%   by weight                                       hexamethylene diamine salt                                                    of the acid of formula (I)                                                                      20%         by weight.                                  


9. A process according to claim 6 wherein n in formula (I) stands forthe number 4, 7, 8 or
 10. 10. A process according to claim 9 wherein nin formula (I) stands for the number 7 or
 8. 11. A process according toclaim 6 wherein polymerisation is carried out at a temperature of 280°to 300°C under a pressure of from 10 to 50 atms.
 12. A process accordingto claim 6 wherein after-condensation is carried out for 1 to 3 hoursunder normal pressure at 250° to 300°C.
 13. The composition of matter asdefined by claim 1, wherein said plasticizer is present in an amount upto about 50% by weight of the total composition.
 14. The composition ofmatter as defined by claim 13, wherein said plasticizer is present in anamount up to about 25% by weight of the total composition.
 15. Thecomposition of matter as defined by claim 1, wherein said plasticizer isselected from the group consisting of a sulfonic acid derivative of theformula ##SPC2##wherein R₁ is hydrogen or methyl and R₂ is hydrogen,lower alkyl or cyclohexyl; a phenol carboxylic acid; a phenol carboxylicacid alkyl ester and bisphenol A.
 16. The composition of matter asdefined by claim 15, wherein said plasticizer is selected from the groupconsisting of benzene sulfonic acid ethyl amide, toluene sulfonic acidethyl amide, butyl-p-hydroxy benzoate, lauryl-p-hydroxy-benzoate,p-oxy-benzoic acid, octyl-p-oxy benzoate and bisphenol A.
 17. Thecomposition of matter as defined by claim 1, further comprising anaqueous dispersant.
 18. The composition of matter as defined by claim17, further comprising a thickener and a stabilizer.